Carbohydrates are the main energy source to living organisms and play important role in different biological functions. However, unlike to the case with other metalloenzymes, the study of metalloenzymes involved in carbohydrate metabolism using synthetic models is largely unexplored. Xylose/Glucose isomerase (XGI) is one example of such enzymes. The long-range plan of this project is to understand the role of the metals at the active site of the enzyme in substrate binding and isomerization. The objective of this application, which is a step in pursuit of that goal, is to synthesize catalytically active complexes with coordination and geometry similar to the metals at the active site of the enzyme. Therefore, efforts toward the synthesis of catalysts and understanding the substrate binding and catalysis in relation to the enzyme's activity are necessary. The central hypothesis of the application is that synthesis and catalytic activity of the model complexes depend on the nature of the ligand and its control on coordination and geometry around the metal centers. This hypothesis has been formulated based on observations reported in the literature for similar ligands and complexes. The rational for the proposed research is that, once model complexes are synthesized and catalytic activity determined, they would be systematically modified to tune their catalytic efficiency. Once the characterization and optimizations are completed, the results will be compared against the data, reported in the literature, on the actual enzyme. Such outcomes will be significant, because the new knowledge is expected to contribute to the understanding of mode of substrate binding and catalysis of the enzyme and possibly other similar carbohydrate metabolic systems.